Question

I have 5 users that all have access to a shared mailbox. The limit of the mailbox is reached and it seems we cannot get more. Apparently they need all emails accessible at all times for every person at the same time. Therefore, a shared PST on a server
is not an option, as only 1 person will be able to open it at the time. This would have appeared to be the most practical option.

Question:

Is there any alternative to storing them on the exchange server and to a PST?

So far what I could think of is,

-dropping them manually in a folder on a server etc., kind of messy...